Polyamine carbamates have been produced in the past by adsorbing the polyamine on a particulate carrier and then reacting the polyamine with carbon dioxide. See Brodoway U.S. Pat. No. 4,102,801.
Another route to carbamate salts is to react an amine in solution with gaseous or dissolved carbon dioxide.
Hexamethylene diamine carbamate has been prepared by the known process of reacting hexamethylene diamine and carbon dioxide in chlorobenzene solvent.
Leon Segal in Applied Spectroscopy Vol. 17, No. 1, 1963 at pages 21-22, discloses the reaction of hexamethylene diamine in the solid state with atmospheric carbon dioxide.
Polyamine carbamates are useful as curing agents for elastomers. The primary diamine carbonates prepared by the process described herein are useful as intermediates for the preparation of polyamides.